Certain medical devices are inserted and/or implanted into the body of a patient to perform a medical procedure. Examples of these devices include catheters, guidewires, medical balloons, stents, and stent-grafts. When a device is advanced through the body, its progress is preferably monitored, e.g., tracked, so that the device can be delivered properly to a target site. After the device is delivered to the target site, the device is preferably monitored to determine whether it has been placed properly and/or is functioning properly.
One method of monitoring a medical device is magnetic resonance imaging (MRI). MRI is a non-invasive technique that uses a magnetic field and radio waves to image the body. In MRI procedures, the patient is exposed to a magnetic field, which interacts with certain atoms, e.g., hydrogen atoms, in the patient's body. Incident radio waves are then directed at the patient. The incident radio waves interact with atoms in the patient's body, and produce characteristic return radio waves. The return radio waves are detected by a scanner and processed by a computer to generate an image of the body, thereby providing information about the placement and/or the functioning of the medical device.